Optical waveguides consist of a transparent waveguiding core surrounded by transparent materials of lower indices of refraction. Several general methods are utilized for the fabrication of optical waveguides.
In one method optical waveguides are formed by applying a dielectric material to a transparent substrate of lower refractive index.
In another method thermoplastic polymer substrates are embossed with a metal die in a desired waveguide pattern, and subsequently filled or coated with a polymerizable higher index liquid monomer.
In another method optical waveguides are formed by selectively altering the index of refraction of a bulk transparent material. One technique involves ion bombardment in which selected regions of increased refractive index are provided by generating a nonlinear disorder pattern in a bulk matrix. In another technique selected regions of increased refractive index are either photo-induced in sensitized polymeric materials such as poly(methyl) methacrylate as described in Appl. Phys. Lett., 16, 486 (1970), or electrically induced by diffusing a higher index dopant into a transparent material.
Optical waveguides fabricated in GaAs/AlGaAs structures by laser-assisted etching has been reported in Integrated And Guided-Wave Optics, 1989 Technical Digest Series, 4, 64-67 (Optical Society of America).
U.S. Pat. No. 4,842,677 describes excimer laser etching of high resolution conductive patterns involving the use of an organic polymeric resist. Other publications relating to photoablation of organic polymers include J. Appl. Phys., 66(3), 1411 (1989).
Methods of fabricating organic waveguides are a newly evolving technology. There are inherent disadvantages in the practice of the various known methods, such as difficult multi-step procedures which do not provide reliable quality control and reproducibility. Typical organic waveguiding devices exhibit high optical scattering losses.
A review article in Journal Of Lightwave Technology, 7(10), 1445 (1989) describes several polymeric channel waveguide fabrication routes, such as etching methods which include wet chemistry etching, reactive ion etching, excimer laser ablation, and the like.
There is continuing interest in the development of new and improved techniques for the fabrication of organic optical waveguides which overcome some of the inherent deficiencies of optical waveguide formation in transparent organic media.
Accordingly, it is an object of this invention to provide an improved method for the production of organic optical waveguides.
It is another object of this invention to provide a method for the production of polymeric optical waveguides by photoablative means.
It is a further object of this invention to provide process embodiments for the production of side chain polymeric optical waveguides which have a two-dimensional channel or rib waveguiding structure.
Other objects and advantages of the present invention shall become apparent from the accompanying description and Examples.